1. Field of the Invention
This invention relates generally to apparatus and processes for water impurity analysis and to impurity analysis of various other liquids as well. More particularly, the present invention concerns apparatus and processes for chemical oxidant and catalyst enhanced total organic carbon analysis of liquid samples for determination of the level of organic contamination of the samples.
2. Description of the Prior Art
In many industrial and laboratory situations an authoritative test is needed for determining the degree of pollution that exists in a liquid, particularly water, stream. Water pollution due to the presence of organic materials has been measured indirectly in BOD analysis by how actively bacteria will use up the organic material in a given sample and consume oxygen from the sample. Since BOD analysis is an exceedingly slow procedure, it has been determined to be more appropriate to measure liquid samples directly for contamination due to the presence and volume of organic materials and to provide a system for rapid and low cost sample analysis. A low cost and rapid analysis process known as Total organic carbon (TOC) analysis has proven quite acceptable for this purpose. Moreover, TOC data can be readily converted to BOD or COD data if desired.
TOC analysis is typically conducted by injecting a known volume of water or other liquid into a furnace containing acid coated quartz chips and being at a sufficient temperature, 150.degree. C., for example, to convert the inorganic carbon in the sample to CO.sub.2 which is then measured by an infrared analyzer that is sensitive to CO.sub.2. Another like volume from the same sample is then injected into a high temperature furnace, 950.degree. C. for example, containing a catalyst to aid complete combustion. Oxygen is then metered into a reaction tube causing the total carbon, inorganic and organic, to be converted into CO.sub.2. The volume of the CO.sup.2 within the sample is then measured by an infrared analyzer. The CO.sub.2 generated by complete combustion is directly proportional to the total carbon in the sample stream. A problem with TOC analysis of this nature is that inaccuracies can result from the coordination of two separate measurements, especially if the ratio of inorganic carbon content of the sample as compared to total carbon is large. The use of a catalyst can also create some problems from the standpoint of accuracy of the TOC analysis being performed.
More recently, TOC analyzer manufacturers have introduced analyzers using a low-temperature ultra-violet (UV) promoted chemical oxidation method which offers certain advantages over combustion TOC analysis. These systems measure TOC directly be means of an acidification and scrubbing pretreatment system which removes carbonates prior to oxidation. The feasibility of the UV/persulfate technique for oxidizing organic carbon was demonstrated a number of years ago and is well documented relative to its excellent oxidation efficiency. The major advantage of a low temperature UV promoted chemical TOC system is that all reactions take place in the liquid phase, resulting in increased reliability and reduced TOC analyzer maintenance requirements.
Total organic carbon analysis is often considered beneficial as a rapid screening method to determine requirements of more costly and time-consuming specific toxic and other organic component analyses. In many cases, depending upon the application, TOC analysis is an adequate and inexpensive substitute for more time consuming and more expensive alternative methods for determination of water quality, provided the TOC analyzer being employed has sufficient sensitivity and capability. These more time consuming and expensive water quality determination methods, for example, include among others, the biochemical oxygen demand (BOD) test and the chemical oxygen demand (COD) test.
It has been determined that titanium dioxide (Ti O.sub.2) is a superior catalyst to aid in the oxidation of organic carbon in water, even at room temperatures, without the aid of any other chemical oxidant. Further enhancement of the carbon oxidation process is accomplished by the use of ultraviolet light impinging on the water sample, typically in the range of from about 3.8 to about 4.3 nanometers. Even further oxidation is accomplished by the chemical addition of sodium persulfate.
It is thus an important feature of the present invention to provided a novel process and apparatus for TOC analysis by which UV light of proper wave length is impinged upon a water sample containing chemical oxidants such as Ti O.sub.2 or sodium persulfate or both.
It is also a feature of the present invention to provide a novel reactor for TOC analysis in which carbon, particularly organic carbon is oxidized to CO.sub.2 gas for further measurement by a CO.sup.2 gas detector, preferably a non-dispersive infrared analyzer.
It is an even further feature of the present invention to provide a novel process for TOC analysis wherein by measuring the CO.sub.2 gas created by combining carbon with oxygen (either in the water, with a carrier gas of oxygen (O.sub.2), or a chemical oxidant, such as sodium persulfate, the carbon in the water sample is determined. Other and further features of the present invention will become obvious and inherent upon review of this disclosure and are considered to be incorporated within the spirit and scope of the present invention.